<template>
  <div class="pagination">
    <h1>{{ startNumAndEndNum }}</h1>
    <button @click="$emit('getPageNo', pageNo - 1)" :disabled="pageNo == 1">
      上一页
    </button>
    <button
      v-if="startNumAndEndNum.start > 0"
      @click="$emit('getPageNo', 1)"
      :class="{ active: pageNo == 1 }"
      :disabled="pageNo == 1"
    >
      1
    </button>
    <button v-if="startNumAndEndNum.start > 2">···</button>
    <!-- 中间连续页码的地方:v-for、数组、对象、数字、字符串 -->
    <button
      v-show="page > startNumAndEndNum.start"
      v-for="(page, index) in startNumAndEndNum.end"
      :key="index"
      @click="$emit('getPageNo', page)"
      :class="{ active: pageNo == page }"
      :disabled="pageNo == page"
    >
      {{ page }}
    </button>
    <button v-if="startNumAndEndNum.end < pageTotal - 1">···</button>
    <button
      v-if="pageTotal > startNumAndEndNum.end"
      @click="$emit('getPageNo', pageTotal)"
      :disabled="pageNo == pageTotal"
    >
      {{ pageTotal }}
    </button>
    <button
      @click="$emit('getPageNo', pageNo + 1)"
      :disabled="pageNo == pageTotal"
    >
      下一页
    </button>
    <button style="margin-left: 30px">共 {{ total }} 条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props: ['total', 'pageSize', 'pageNo', 'continues'],
  computed: {
    pageTotal () {
      return Math.ceil(this.total / this.pageSize)
    },
    startNumAndEndNum () {
      const { total, pageSize, pageNo, continues } = this
      // 定义两个变量，存储起始数字与结束数字
      let start = 0, end = 0
      // 不正常现象【总页码没有连续页码多】
      if (continues >= this.pageTotal) {
        start = 1
        end = this.pageTotal
      } else {
        start = pageNo - parseInt(continues / 2)
        end = pageNo + parseInt(continues / 2)
        // 纠正不正常现象【start数字出现0|负数】
        if (start < 1) {
          start = 1
          end = continues
        }
        // 纠正不正常现象【end数字大于总页码】
        if (end > this.pageTotal) {
          end = this.pageTotal
          start = this.pageTotal - continues + 1
        }
      }
      return { start, end }
    }
  },
  methods: {
  }
}
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #1c3c7a;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>
